Electromagnetic relay



March 10, 1959 R. L. PEEK, JR 2,877,316

ELECTROMAGNETIC RELAY Filed June 19, 1956 /NVE/v Tof? By R. L. PEE/ JR.

A 7' TORNE V United States Patent() ELECTROMAGNETIC RELAY Robert L. Peek, Jr., New York, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 19, 1956, Serial No. 592,369

7 Claims. (Cl. 200`S7) This invention relates to circuit controlling devices and, more particularly, to such devices of the type commonly referred to as reed switches.

It is frequently necessary in certain electrical systems to operate a switching device and to hold it so operated for a considerable period of time. In existing systems this is usually accomplished by maintaining an electrical current in an energizing winding of a device such as disclosed in Patent 2,289,830, issued July 14, 1942, to W. B. Ellwood, for the duration of the desired period of contact engagement. Frequently, however, it has been found to be difficult or expensive to supply adequate power to the system for the purpose of furnishing the current necessary to maintain such devices in an operated condition. Although the current required by an individual device of the Ellwood type is relatively small, it becomes of considerable consequence when multiplied by the large number of such devices that are ordinarily used in these systems.

Heretofore, it has been possible in certain instances to reduce to some extent the adverse effects of this large power requirement. For example, the energizing current in the windings of the individual switching devices can be reduced to a` hold value after the switch contacts have been operated, or a permanent magnet or mechanical holding means may be used for this purpose. For the most part, however, devices using these types of holding means have not been commercially successful either because of their high manufacturing cost or because the means used to maintain the contacts in an operated position have had certain adverse effects on the otherwise Aexcellent operating characteristics of devices of the Ellwood type.

One general object of this invention is to improve circuit controlling devices of the type wherein magnetic contact members are employed to open or close a conductive path.

More specifically, some objects of this invention are to enable the device to operate when energized by an electrical current and tol remain in an operated condition after the energizing current is removed, to permit one Contact pair to operate and another contact pair to `release when a winding encircling both pairs is energized by a current in a given direction, to minimize chatter, and to reduce the current requisite for operation of such devices.

Additional objects of this invention are to accomplish the foregoing without the necessity for permanent magnets or mechanical hold means, to facilitate fabrication and simplify the structure of such devices and to reduce the size of circuit controlling devices capable of per:- forming multiple functions, for example, make and break4 of plural circuits.

In one illustrative embodiment of this invention ay switching device comprises a switch unit including a. switch envelope and two contact members enclosed in.

said envelope, a sleeve of highly retentive magnetic rna-y terial disposed about said envelope, andan energizing i Patented Mar. 10, 1959 winding surrounding said sleeve for substantially the entire length thereof.

In another illustrative embodiment of this invention a switching device comprises a switch unit of the above type, a first sleeve of highly retentive magnetic material disposed about one of the contact members at one end of the switch envelope, a second sleeve of highly retentive magnetic material disposed about the other contact members at the other end of the envelope, and an energizing winding disposed about substantially the entire length of both sleeves.

In accordance with one feature of this invention the magnetic flux from the magnetically retentive sleeve or sleeves, after energization of the winding by current in a given direction, will provide a strong magnetic field that will hold the contact members in an operated position after the energizing current is removed. The contact members may be returned to their unoperated position by applying current to the Winding in the opposite direction. This feature is accomplished without the use of permanent magnets or mechanical holding means in the switch structure.

In accordance with another feature of this invention each of the above described embodiments may be placed axially inside of a single energizing winding to provide out-of-phase operation. Thus, at least after a single operation, the contact members in one of the switch units Will operate and remain operated, when the Winding is energized by current in a forward direction and then deenergized, while the contact members in the other switch unit will release. When the winding is energized by current in the opposite or reverse direction, the contact members in the one switch unit will release while the contact members in the other switch unit will operate and Will remain operated after the Winding is deenergized.

In accordance with a further feature of the invention, the residual magnetism remaining in the magnetically retentive sleeve or sleeves will produce forces across the contact gap which will aid the forces created by the energizing coil in causing the contact members to operate. Consequently, high forces are realized across this gap, and the device will operate on a minimum amount of current in the winding and will be relatively free from the deleterious effects of chatter.

The above-noted and other features of the invention will be understood more clearly and fully from the following detailed description, when read in conjunction with the accompanying drawings, in which:

Fig. l is a longitudinal view, partially in cross-section, illustrative of one embodiment of the invention;

Fig. 2 is a longitudinal view, partially in cross-section, illustrative of another embodiment of the invention; and

Fig. 3 is a longitudinal view, partially in cross-section, illustrative of a third embodiment of the invention.

Referring to Fig. 1 of the drawings, there is shown the preferred structure and assembly of the invention. The switching element of the device comprises a switch unit 1t), which may be of any suitable type but which preferably comprises a glass envelope 11 and reed contact members 12 and 13. These contact members are sealed in the envelope 11 at each end thereof and overlap in spaced relation to each other at the approximate center of the envelope 11 to form contact areas 14 and 15. The members 12 and 13 retain suflicient natural resilience to tend to assume the unoperated positions shown in Fig. 1. In .all of the disclosed embodiments of the invention the contact members 12 and 13 have been fabricated from a lat Permalloy reed, but it will be readily apparent that .other materials may be used having other cross-sectional configurations providing the desired electrical and magnetic properties are retained. The contact areas 14 and 15 may be plated with gold or other precious metal and the envelope 11 may be filled with an inert gas in order to improve the over-all operating characteristics of the device. However, this is by no means essential for successful operation thereof.

A first sleeve 16 surrounds the contact member 12 at one end of the envelope 11, and a second sleeve 17 surrounds the contact member 13 at the other end of the envelope 11. The sleeves 16 and 17 are made of highly retentive magnetic material, such as high carbon steel, and for most applications they should be spaced a sufficient distance apart so that they do not extend around the contact areas 14 and 15.

It is important during the operation of the device that the magnetic ux passing directly from one sleeve to the other be kept at a relatively low value. Consequently, these sleeves should be kept a sufficient distance apart to avoid this magnetic interference. It has been found that the most desirable operating characteristics are attained when the sleeve separation is equal to or greater than the radial distance from one of the contact members 12 or 13 to its corresponding sleeve 16 or 17; or, approximately one-half the inside diameter of the sleeves. However, for some applications the device will operate effectively when the distance between the sleeves is approximately equal to the amount of overlap of the contact members 12 and 13.

An energizing winding 18 having leads 21 and 22 surrounds the switch unit 16 and preferably encompasses a substantial portion of each of the sleeves 16 and 17. The winding 18 may be held in position by means of an insulating spoolhead 19; and, if desired, a magnetic cover 20 may be disposed about the outside of the winding 18 in order to provide a magnetic return path for the flux emanating from the sleeves 16 and 17 and for the ux produced by the winding 13. However, it will readily be apparent to those skilled in the art that for some applications the spoolhead 19 and the cover 20 may be omitted without departing from the spirit and scope of the invention.

Other detaiis will be understood from the following description of the mode of operation of the device.

When an energizing current is applied to the leads 21 and 22 of the winding 18 in a forward direction, a magnetic flux will be created that will follow two parallel paths. One of these paths flows in a direction from the left end of the winding 18 as viewed in Fig. 1, for eX- ample, axially through the contact member 13, across the gap between the Contact area 14 and the contact area 15, through the contact member 12 and then back along the cover 20 to complete one magnetic circuit. The other of these paths ows in a direction from the left end of the winding 1S, through the sleeve 17, from the sleeve 17 'to Vthe contact member 13 and its corresponding contact area 14, across the contact gap between the contact area 14 and the Contact area 15 to the contact member 12, from the contact member 12 to the sleeve 16, through the sleeve 16 and then back along the cover 20 to cornplete another magnetic circuit. Of course, there may be a certain amount of leakage ux passing directly from the sleeve 17 to the sleeve 16 without crossing the contact gap, but the adverse effects of this leakage flux may be reduced to a negligible amount by maintaining a sufficient separation between the sleeves, as has been indicated heretofore. The combined effect of these two flux paths across the contact gap between areas 14- and 15 causes the contact members 12 and 13 to come in contact with each other, thereby Closing an electrical circuit.

When the forward energizing current is removed from the leads 21 and 22, electromagnetic flux will no longer follow the first of the above flux paths. However, the residual magnetism remaining in the sleeves 16 and 17 will produce a flux that is suflicient to maintain the contact members 12 and 13 in an operated position. This ux will follow the second of the above flux paths, and :the forces created thereby will rmly hold the contact members 12 and 13 in electrically conductive relation. Largely because of the magnetically aiding relationship between the sleeves 16 and `17, a tight connection is provided without the necessity for supplying current to the winding 18 or for employing permanent magnets or mechanical holding means and this connection is substantially unaffected by jarring or other vibration of the device.

In order to return the contact members 12 and 13 to their initial unoperated position, current is applied to the winding leads 21 and 22 in a reverse direction. The amount of current necessary for this purpose need not be as great as that required for the initial or forward operation, and preferably the reverse current is at a substantially lower value which may be of the order of iive to ten percent of the forward current. The reverse current in the winding 1S creates an electromagnetic flux that follows a path from the right end of the winding, for example, along the contact member 12, across the gap between the contact areas 15 and 14, through the contact member 13 to the left end of the winding and back through the cover 29 to the starting point. The reverse current will tend to cause a flux flow through the sleeves 16 and 17; but, due to the relatively small value of this reverse ux compared to the residual forward flux produced by the sleeves, the residual forward flux will remain substantially the same. This situation produces an effect at the gap between the contact areas 14 and 15 of opposing uxes. The forward residual flux, which was holding the contact areas 14 and 15 closed to each other, is thus reduced at this contact gap by the reverse flux from the winding such that the contact members release from each other.

Referring now to Fig. 2 of the drawings, there is shown a second illustrative embodiment of the invention. This embodiment is similar in most respects to the first embodiment in that a switch unit 1t) is contained by spool heads such as 19, a winding 18 and a cover 2t). However, a single sleeve 23 of magnetically retentive material has been used in place of the two sleeves 16 and 17 of Fig. l, and the sleeve 23 surrounds the envelope 11 for substantially the entire length thereof.

When an energizing current is applied to the winding leads 21 and 22 of the device shown in Fig. 2 in a forward direction, an electromagnetic flux is created which will follow two parallel paths. The first of these flux paths extends from the left end of the winding 18, for example, along the contact member 13 to the Contact area 14, across the contact gap between the contact area 14 and the contact area 15, from the contact area 15 to the contact member 12, and then back through the cover 20 to complete a rst magnetic circuit. The forces created by the electromagnetic flux across the contact gap are sufficient to cause the contact members 12 and 13 to come in contact with each other, thereby closing an electrical circuit. The second flux path extends from the left end of the winding 18, for example through the sleeve 23 to the right end of the winding 18, and then back along the cover 20 to complete a second magnetic circuit. It will readily be apparent that this second magnetic flux has little appreciable effect on the contact members 12 and 13 but will cause the sleeve 23 to become magnetized.

When the forward energizing current is removed from the leads 21 and 23, electromagnetic linx will no longer follow the first of the above ux paths. However, vsince the sleeve 23 retains an appreciable amount of residual magnetism, it will create a magnetic flux that follows a path from the right end of the sleeve 23, for example, and through the contact members 12 and 13 to the left end of the sleeve. This flux is insufficient to cause the contact members 12 and 13 to operate but is suiicient to hold them in their operated position. Since the flux from the sleeve 23 ows through the contact members 12 and 13 in a direction opposite to that of the initial operate flux created by the winding 18, the net `amount of ux across the contact gap when the energizing current is removed will reduce to zero and will actually begin to build up in an opposite direction. Asa.: this flux across the contact gap approaches zero, the natural resiliency of contact members 12 and 13 will cause them to return to their initial or unoperated position. As has been pointed out previously, the flux across the contact 4gap will build up in an opposite direction, but this ux is insuicient to cause the contact members 12 and 13 to come in contact with each other. Consequently, the device returns to its unoperated position.

In order to insure that the contact members 12 and 13 open when the forward current is removed from the winding 18, it may be necessary to delay the decay and subsequent build-up of the flux from the sleeve 23. Thus, if this flux across the contact gap changes direction too rapidly, the contact members 12 and 13 will not have sufficient time to open and will be held in their operated position by the forces created by the sleeve flux. As shown in the embodiment illustrated in Fig. 2, an additional sleeve 24 of copper'foil is disposed between the magneticallylretentive sleeve 23 and the-envelope 11 for the purpose of delaying the decay and subsequent buildupof the flux emanating from the sleeve 23. Consequently, the opening of contact members 12 and 13 during the interval of linx reversal is insured. Other means known to the art may be employed for delaying the ilux decay and subsequent build-up, and for same application the I"delaying means may be omitted entirely without departing from the spirit and scope of the invention. j `When a smaller reverse current is applied to the leads 21 and 22 of Fig. 2, an electromagnetic ux will be created bythe winding 18 which will follow a path from the right end of winding 18, for example, through the contact member 12 to the contact area 15, across the contact gap between the contact area 15 and the contact area. 14, from the Contact area 14 to the contact 13 and then back along the cover 20 to complete a magnetic circuit. Furthermore, although the reverse current tends to partially demagnetize the magnetically retentive sleeve 23 the sleeve 23 retains suicient residual magnetism, due to the smaller reverse current, to maintain a certain amount of flux flowing from the contact member 12 to the contact member 13. The combined effect of the electromagnetic ux from the winding 18 and the residual magnetic flux from the sleeve 23 causes the contact members 12 and 13 to corne in contact with each other and thus reclose the electrical circuit.

When the reverse current is removed from the leads 21 and 22, the electromagnetic flux provided by the winding 18 will no longer continue to flow between the contact members 12 and 13. However, the remaining flux from the magnetically retentive sleeve 23 will be of sucient strength to maintain the contact members 12 and 13 in their operated position. Thus, an electrically conductive path exists between the contact member 12 and the contact member 13 even though there is no current in the winding 18, and this has been accomplished without the necessity for permanent magnets, etc.

The device of Fig. 2 is returned to its unoperated (contacts open) condition by applying energizing current to the winding leads 21 and 22 in an initial or forward direction. This will create an electromagnetic flux in the winding 18 which will follow a path from the left end of winding 18, for example, through the contact member 13 and contact area 14, across the gap between contact area 14 and contact area 15 to the contact member 12 and then back along the cover 20 to complete a magnetic circuit. Energization of the winding `18 in this forward direction will also function to restore the sleeve 23 to its fully magnetized condition. Consequently, when the forward energizing current is removed, the direction of flux across the contact gap will reverse in direction, and, as previously explained, this reversal will cause contact members 12and 13l to disengage, thereby opening the electrical circuit.

From the above, at least ai ter an initial forward energization, it will be apparent that the embodiment of the invention as disclosed in Fig. 2 will operate when energized by a reverse current and will remain operated after this reverse current is removed. This embodiment will operate when energized by current in a forward direction and will release after this forward current is removed. The amount of forward or reverse current necessary for operation of this type is extremely small, and high forces are realized across the contact gap which greatly minimize the deleterious effects of'chatter.

Referring now to Fig. 3 of the drawings, there is disclosed a third embodiment of the invention wherein two of the switch units 10 and 10 have been enclosed in a single winding 25 having spoolheads 26 of insulating material and a magnetic cover 27. One Iof the switch units 10 is provided withtwo magnetically retentive sleeves 16 and 17 which are arranged similarly to the sleeves shown in Fig. l; while, the other of the switch units 10 is provided with a single magnetically retentive sleeve 23 and a copper foil sleeve 24 in a manner similar to that shown in Fig. 2.

As will be apparent with reference to the above description of the operation `of the invention in accordance with the Fig. 1 embodiment and-with the Fig. 2 embodiment, energization of the winding 25 by current applied to leads 28 and 29 in a forward direction will cause the contact members 12 and 13 in the upper switch unit 10 to operate and to remain in an operated position after the forward energizing current is removed. The contact members 12 and 13 in the lower switch unit 10', however, will be in an unoperated position after this forward current is removed. When the winding 25 is energized and then deenergized by current in a reverse direction, the contact members12 and 13 in the upper switch unit 10 will return to their unoperated position while the contact members 12 and 13 in the lower switch unit 10 will operate and will remain in an operated position after the energizing current is removed. Thereafter, energization and deenergization of the winding 25 by the application of suitable current to the leads 28 and 29 in -a given direction will cause the contact members in one of the switch units of Fig. 3 to operate and to remain in an operated position after the energizing current is removed while the contact members in the other switch unit will return to their unoperated position. Thus, in accordance with this embodiment of the invention, out-of-phase operation has been provided that can be yadapted to close one electrical circuit and open another upon the energization and deenergization of a single electromagnetic winding by current in a given direction.

Although several specic embodiments of the invention have been shown and described, it will be apparent that the various modifications of the component parts of these embodiments are, in certain instances, interchangeable with each other and that certain of the mechanical and electrical details shown may be modified without departing from the scope and spirit of the invention.

What is claimed is:

1. A switching device comprising a switch unit including an elongated tubular envelope and two contact members of magnetic material sealed in and extending through respective ends of said envelope, the inner ends of said members comprising contact areas overlapping substantially in the center of said envelope in spaced relation to each other, a first sleeve of highly retentive magnetic material surrounding one end of said envelope for substantially the entire length of one of said members except the contact area thereof, a second sleeve of highly retentive magnetic material surrounding the other end of said envelope for substantially the entire length of the other of said members except the contact area thereof,

and an energizing winding surrounding both of said sleeves and said contact areas, said winding extending lengthwise so as to surround substantially the entire length of said envelope.

2. A switching device comprising a switch unit including two contact members in operable relation to each other, a highly retentive magnetic member disposed about said switch unit and about both of said contact members, and energizing means disposed about both said highly retentive magnetic member and said contact members.

3. A switching device comprising a switch unit including two contact members in operable relation to each other, a highly retentive magnetic sleeve disposed about said switch unit and about both of said contact members, and energizing means disposed about said sleeve for substantially the entire length of said sleeve.

4. A switching device comprising a switch unit including an elongated envelope `and two contact members enclosed in and extending through respective ends of said envelope, the inner ends of said members comprising contact areas overlapping in spaced relation to each other, a sleeve of highly retentive magnetic material disposed about said switch unit so as to surround both of said contact members for substantially the entire length of said members, and energizing means disposed about both of said contact members for substantially the entire length of said envelope.

5. A switching device comprising a switch unit including two resilient spaced contact members in operative relation to each other, said members tending, because of a restoring force arising from their resiliency, to assume their spaced condition when moved into contacting relation with each other, magnetically retentive sleeve means disposed about said switch unit for exerting a counterforce greater than said restoring force, and energizing means disposed about both of said contact members, whereby lock-up operation of said switching device is provided.

6. A switching device comprising a switch unit inI cluding two contact members in operative relation tto each other, energizing means disposed about said contact members, and means for providing lock-up operation of said members, said means including cylindrical magnetically retentive means disposed about said switch unit.

7. A switching device comprising a switch unit including an elongated envelope and two resilient contact members enclosed in and extending through respective ends of lsaid envelope, the inner ends of said members comprisf ing contact areas overlapping in spaced relation to eac'h other, said resilient members exerting a force to restore said inner ends to a spaced condition whenever said ends are brought into contacting relation with each other, lenergizing means disposed about said envelope for substantially the entire length thereof, and a sleeve of highly retentive magnetic material disposed about said switch unit for more than opposing said restoring force and so providing lock-up operation of said device.

References Cited in the le of this patent UNITED STATES PATENTS 668,022 Shreeve Feb. 12, 1901 1,475,166 Beall et al. Nov. 27, 1923 1,920,764 Nickle Aug. 1, 1933 2,027,064 Rozumek Ian. 7, 1936 2,167,588 Rozumek July 25, 1939 2,187,115 Ellwood et al. Ian. 16, 1940 2,277,215 Ellwood Mar. 24, 1942 2,289,830 `Ellwood July 1.4, 1942 2,378,986 Dickten June 26, 1945l 2,397,123 Brown Mar. 26, 1946 2,678,360 Bellis May 11, 1954 FOREIGN PATENTS 431,233 Great Britain July 3, 1935 

